In many automotive vehicles having electric parking brakes, the electric parking brake is applied if it is detected that the driver is not present and the vehicle is in gear. One such example is a control known as “SafeHold” that a number of vehicles available from FCA US LLC have. This SafeHold control uses a number of inputs to determine whether to apply the electric parking brake due to lack of driver presence when the vehicle is in a state that might allow the vehicle to move. More specifically, SafeHold control uses vehicle speed, transmission position, accelerator pedal position, brake pedal position, seat belt condition, and driver door position to determine whether to apply the electric parking brake due to lack of driver presence in the vehicle.
With reference to FIGS. 1 and 2, a basic method by which the SafeHold control determines to apply the electric parking brake due to lack of driver presence is described. FIG. 1 is a simplified schematic representation of an automotive vehicle 100 having an electric parking brake and an electronic control unit. The electronic control unit will be referred to herein as ECU 102 and the electric parking brake will be referred to herein as EPB 104. ECU 102 is configured to control EPB 104 including being configured to implement the SafeHold feature. It should be understood that ECU 102 may be an ECU that controls other aspects of the vehicle as well as EPB 104. In an example, ECU 102 is the electronic control unit for an electronic stability system of vehicle 100.
The schematic of FIG. 1 shows the inputs to ECU 102 used by the SafeHold control in whether to apply EPB 104 due to lack of driver presence in vehicle 100. These inputs include a driver door open/closed input which will be referred to herein as driver door ajar input 106, a driver seat belt buckled/unbuckled input 108, a brake pedal position input 110, a throttle pedal position input 112, an ignition switch position input 114, a transmission PRNDL position input 116 and a vehicle speed input 118. Driver door ajar input 106 receives a signal that indicative of indicates whether a driver door 107 of vehicle 100 is ajar. Driver seat belt buckled/unbuckled input 108 receives a signal indicative of whether a driver seat belt 109 of vehicle 100 is buckled or unbuckled. Brake pedal position input 110 receives a signal indicative of whether a brake pedal 111 of vehicle 100 is at rest, for example a signal indicative of brake pressure wherein brake pressure being above a predetermined threshold is indicative that the brake pedal has been pushed and being below the predetermined threshold is indicative of the brake pedal being at rest. Throttle pedal position input 112 receives a signal indicative of whether a throttle pedal 113 of vehicle 100 is at rest. Ignition switch position input 114 receives a signal indicative of whether an ignition switch 115 of vehicle 100 is in a run position. Transmission PRNDL position input 116 receives a signal (or signals) indicative of whether a transmission 117 of vehicle 100 is in any of reverse, neutral or drive. Vehicle speed input 118 receives a signal indicative of a speed of vehicle 100. In this regard, that It should be understood that each of these inputs are provided by known devices in vehicle 100, which can be different types of sensors, switches or other devices as is known to those skill in the art. It should also be understood that these devices may be directly coupled to ECU 102, coupled to ECU 102 over a bus such as a CAN bus, coupled to other electronic control devices in the vehicle such as a body controller electronic control unit or an engine controller electronic control unit which then communicates their status to ECU 102, or any combination of the foregoing. It should be understood that the control of EPB 104 that ECU 102 is configured to implement may utilize other inputs for the control of EPB 104 for aspects of the control of EPB 104 other than the SafeHold control.
FIG. 2 is a flow chart of a software control program that is programmed in ECU 102 that configures ECU 102 to implement the SafeHold control. It should be understood that when it is stated that the control program performs a function, it means that ECU 102 is configured by the control program to perform the function. The control program starts at 200. At 202, the control program checks whether the driver door of vehicle 100 is open. If the driver door is open, the control program proceeds to 204 and if not, the control program branches back to 200. At 204 the control program checks whether the driver seatbelt is unbuckled. If the driver seat belt is unbuckled, the control program proceeds to 206 and if not, the control program branches back to 200. At 206, the control program checks whether the brake pedal of vehicle 100 is at rest (that is, whether the brake pedal is not depressed). If the brake pedal is at rest, the control program proceeds to 208 and if not, the control program branches back to 200. At 208 the control program checks whether the throttle pedal is at rest (that is, whether the throttle pedal is not depressed). If the throttle pedal is at rest, the control program proceeds to 210 and if not, the control program branches back to 200. At 210, the control program checks whether the ignition switch of vehicle 100 is in the run position. If the ignition switch is in the run position, the control program proceeds to 212 and if not, the control program branches back to 200. At 212, the control program checks whether the transmission of vehicle 100 is in a position that would allow vehicle 100 to move such as in reverse, neutral, drive or low such as by checking whether the PRNDL position is in reverse, neutral, drive or low. If the transmission is in a position that would allow vehicle 100 to move, the control program proceeds to 214 and if not, the control program branches back to 200. At 214, the control program checks whether vehicle 100 is traveling at a speed less than 5 KPH. If vehicle 100 is traveling at a speed less than 5 KPH, the control program proceeds to 218, and if not, the control program branches back to 200. At 218, the control program applies the SafeHold control and applies EPB 104 which applies the parking brake function provided by EPB 104 to brake vehicle 100. The control program then proceeds to end at 220.
To summarize, the control program applies EPB 104 due to lack of driver presence when it determines that the driver door is ajar, the driver seatbelt is unbuckled, the brake pedal is at rest, the throttle pedal is at rest, the ignition switch is in the run position, the transmission is in a position that would allow vehicle 100 to move (such as run, neutral, drive or low), and vehicle 100 is traveling at a speed less than 5 KPH. In some cases, the foregoing has resulted in a false positive where the control program has determined lack of driver presence and activated EPB 104 when the driver is still present in the vehicle.